Memory devices are typically provided as internal, semiconductor, integrated circuits and/or external removable devices in computers or other electronic devices. There are many different types of memory including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), flash memory, and resistive (e.g., resistance variable) memory, among others. Types of resistive memory include programmable conductor memory, phase change random access memory (PCRAM), resistive random access memory (RRAM), magnetoresistive random access memory (MRAM; also referred to as magnetic random access memory), and conductive-bridging random access memory (CBRAM), among others.
Memory devices can be utilized as volatile and non-volatile memory for a wide range of electronic applications in need of high memory densities, high reliability, and low power consumption. Non-volatile memory may be used in, for example, personal computers, portable memory sticks, solid state drives (SSDs), personal digital assistants (PDAs), digital cameras, cellular telephones, portable music players (e.g., MP3 players) and movie players, among other electronic devices. Data, such as program code, user data, and/or system data, such as a basic input/output system (BIOS), are typically stored in non-volatile memory devices.
Resistive memory such as RRAM includes resistive memory cells that can store data based on the resistance state of a storage element (e.g., a resistive storage element having a variable resistance). As such, resistive memory cells can be programmed to a desired data state by varying the resistance level of the resistive storage element. Resistive memory cells can be programmed to a desired data state (e.g., corresponding to a particular resistance state) by applying sources of energy, such as positive or negative electrical pulses (e.g., positive or negative voltage and/or current pulses) to the cells (e.g., to the resistive storage element of the cells) for a particular duration.
One of a number of data states (e.g., resistance state) can be set for a resistive memory cell. For example, a single level cell (SLC) may be programmed to one of two data states (e.g., logic 1 or 0), which can depend on whether the cell is programmed to a resistance above or below a particular level. As an additional example, various resistive memory cells can be programmed to multiple different resistance states corresponding to multiple data states. Such cells may be referred to as multi state cells, multi-digit cells, and/or multilevel cells (MLCs), and can each store data having values of multiple binary digits (e.g., 10, 01, 00, 11, 111, 101, 100, 1010, 1111, 0101, 0001, etc.).
Some arrays of resistive memory cells can include a one transistor one resistor (1T1R) architecture in which each memory cell includes one access device and one resistive storage element. In such 1T1R architectures, adjacent resistive storage elements can be electrically separated from each other using shallow trench isolation (STI). In some 1T1R architectures, isolation transistors can be used to selectively electrically separate adjacent resistive storage elements (e.g., instead of STI).